The present invention relates to the alkylation of aromatic compounds by the use of novel magnesium silicates. In particular, the present invention relates to the alkylation of a mixture of aromatic compounds by the use of novel magnesium silicates having a porous structure and catalytic properties.
Processes for the alkylation of aromatic compounds and particularly, processes for the ethylation of toluene are well-known, see e.g., U.S. Pat. No. 4,086,287, and references cited therein. Catalysts for the reaction include those generally referred to as zeolites such as the ZSM-5 type zeolite catalysts and similar crystalline aluminosilicates such as those disclosed in the above U.S. Pat. No. 4,086,287.
It is also known to alkylate aromatic compounds such as benzene and toluene by reaction with olefins, especially ethylene, using Friedel-Crafts catalysts, especially AlCl.sub.3, under alkylating conditions.
Previously known processes have satisfactorily been employed to alkylate individual aromatic compounds. However, relatively pure sources of aromatic compounds have heretofore been employed. In particular, it has not been previously suitable to alkylate a mixture of benzene and toluene containing appreciable amounts, e.g., greater than about 1 percent by weight, of either component due to the formation of appreciable amounts of xylenes due to the disproportionation of alkyltoluene at elevated temperatures. A preferred temperature range for the alkylation of benzene using prior art processes lies above about 100.degree. C. At higher elevated temperatures, the ethylation of toluene produces significant amounts of xylenes in addition to the desired ethyltoluene product.
Where the desired product is to be dehydrogenated to yield vinyltoluene or styrene, it is necessary to remove xylenes and other contaminants prior to the dehydrogenation reaction. Such a separation is extremely difficult due to the fact that ethylbenzene and p-xylene differ in boiling points by only 2.2.degree. C. Such a narrow temperature differential requires the use of extremely expensive distillation towers and the consumption of large amounts of heat energy to result in favorable xylene levels. These requirements would add unacceptable costs to the total system. As a result, at the present time it is commercially impractical to alkylate a mixture of aromatic compounds. In particular, it is presently commercially unsuitable to alkylate a mixture of toluene and benzene.